Surgical mesh and method

ABSTRACT

Disclosed is a continuously knitted tubular surgical mesh of monofilament threads free of water-leachable irritant impurities and physiologically inert even in the presence of infection, the threads being unattached at their points of crossing each other. Also disclosed are methods of using the surgical mesh in which the mesh is flattened thereby providing continuous knitted border edges on each side of the mesh, free of selvedge edges, which prevent unraveling or fraying of the border edges and at the same time avoid retaining any infection present by the border edges. Even though doubled, the tubular surgical mesh permits a greater porosity which allows substantially improved growth of tissues through it, it has greater stretch and flexibility than prior flat surgical meshes, and it avoids retaining infection or contamination by a selvedge edge. It also has increased tensile strength and improved flexural properties over prior flat meshes.

This is a division of application Ser. No. 157,146 filed June 6, 1980,now U.S. Pat. No. 4,347,847.

BACKGROUND OF THE INVENTION

A knitted mesh of polypropylene monofilament has been used for manyyears as a prosthesis for the repair of hernias and to close defects inthe abdominal and chest walls.

The knitted mesh has been resistant to infection because of the open,porous construction of the weave and because it is made frommonofilament rather than a braided yarn. Tissue grows to some extentthrough the mesh quite rapidly and it serves as an excellentreinforcement for the tissues.

The knitted mesh is frequently used in strips measuring one inch, twoinches and ten inches in width. A selvedge edge, usually braided dacron,is provided on both edges of the strips to prevent unraveling or frayingof the mesh at the edges. This is very important because in herniarepair, sutures are placed through the mesh at the two borders to secureit to the tissues and frequently considerable tension is exerted on theborder of the mesh. Selvedge edges cannot be placed on the two ends ofthe mesh strip because it has to be cut to size (crosswise) according tothe size of the defect.

If the wound becomes infected, the selvedge edge retains infectionbecause of the multiple filament yarn construction of the selvedge edge.This results in prolongation of the wound infection and frequentlyinfected draining sinus tracts originating from the selvedge edgedevelope. This requires further surgery to remove the infected selvedgeedge.

Examples of such knitted surgical mesh and methods of repairing bodytissues with such surgical mesh are disclosed in my prior U.S. Pat. Nos.3,054,406 and 3,124,136. In addition, Davol. Inc. has been marketingmonofilament polypropylene mesh with selvedge edges under the Trademark"Davol/Usher's Marlex Mesh" as described above for many years.

It would be highly desirable to provide a knitted surgical mesh ofgreater porosity allowing better growth of tissue through it, one whichis free of selvedge edges thereby avoiding retention of contamination orinfection, and a mesh of greater strength and flexibility than priorsurgical meshes. It is not possible to increase the porosity of priorflat surgical meshes because to provide a mesh of more open weave, thediameter of the threads would have to be increased which would make themesh too stiff for practical use. Polypropylene mesh having amonofilament diameter of 6 mils and 68 stitches or courses to the inchis presently in use, and to make an open weave would require too large amonofilament diameter and thus provide too stiff a mesh.

SUMMARY OF THE INVENTION

The present invention is directed to a surgical mesh which is knitted incontinuous tubular shape, free of selvedge edges, which in use isflattened and the mesh is sutured through the continuous border edges tothe tissue, such as for the repair of hernias and to close defects inthe abdominal and chest walls.

The tubular surgical mesh can be of greater porosity thereby allowingbetter growth of tissue through it, even when doubled, and it hasgreater stretch and flexibility because of its greater porosity or openor loose weave than prior surgical meshes. It avoids contamination atits edges since there are no braided selvedge edges as in prior surgicalmeshes.

The mesh may be made of any suitable monofilament threads free ofwater-leachable irritant impurities and which are physiologically inerteven in the presence of infection. Suitable materials are knitted orwoven tubes of polypropylene, dacron, teflon, or polyethylenemonofilament.

The method comprises repairing of hernias by suturing the tubularsurgical mesh to the tissues in flattened form by suturing through itscontinuous border edges to tissue adjacent and bridging the hernialdefect, the tubular surgical mesh having sufficient openings even whendoubled to permit rapid tissue growth through it.

Accordingly, it is an object of the present invention to provide asurgical mesh knitted in continuous tubular shape, free of selvedgeedges, which in use is flattened and the mesh is sutured through thecontinuous border edges to the tissue adjacent and bridging the hernialdefect.

It is a further object of the present invention to provide a surgicalmesh of greater porosity thereby promoting better growth of tissuethrough it than prior surgical meshes.

It is a further object of the present invention to provide such asurgical mesh which has greater strength and stretch than prior surgicalmeshes.

A further object of the present invention is a surgical mesh which isfree of selvedge edges yet the edges of the mesh do not fray or unravelwhen sutured at its edges adjacent to and bridging the hernial defect.

A further object of the present invention is the provision of acontinuously knitted tubular surgical mesh of monofilament threads beingunattached at their points of crossing, which, in use, is flattenedthereby providing continuous knitted border edges on each side of themesh, thereby avoiding the use of selvedge edges to prevent unravelingor fraying of the border edges, and which thereby avoids retaining anyinfection or contamination along the selvedge edges.

Other and further features, objects and advantages are set forththroughout the specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph on a magnified scale (6x) of a portion of anactual surgical mesh strip of the prior art provided with selvedgeedges.

FIG. 1A is a further magnified (16x) of a portion of the mesh of FIG. 1.

FIG. 2 is a magnified (6x) photograph of a portion of a tubular knittedsurgical mesh according to the invention.

FIG. 2A is a further magnified (16x) photograph of the tubular surgicalmesh of FIG. 2.

FIG. 3 is an example of the use of the tubular mesh of the presentinvention in the repair of an incisional hernia.

FIG. 4 is a view similar to that of FIG. 3 illustrating a further stepin the use of tubular surgical mesh of the invention in the repair of anincisional hernia.

FIG. 5 is a view similar to that of FIG. 4 illustrating the closing ofthe anterior fascia completing the repair.

FIG. 6 is a photograph of the use of the prior art surgical mesh ofFIGS. 1 and 2 to repair an incisional hernia on the left side of a dog.

FIG. 6A is a photograph the same as that of FIG. 6 taken eighteen dayslater.

FIG. 7 is a photograph of the use of the tubular surgical mesh of FIGS.2 and 2A in the repair of an incisional hernia on the right side of adog.

FIG. 7A is a photograph of the repaired incisional hernia illustrated inFIG. 7 taken eighteen days later and illustrating tissue growthcompletely through the surgical mesh.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 1A, a knitted surgical mesh of the priorart is illustrated. In order to prevent fraying or unraveling of theedges subject to tension by sutures in use, selvedge edges are providedon each side or border of the surgical mesh. This is very importantbecause in hernia repair, sutures are placed through the mesh at the twoborders to secure it to the tissues and frequently considerable tensionis exerted on the border of the mesh. Selvedge edges cannot be placed onthe two ends of the mesh strip because it has to be cut to size, that iscross-wise, according to the size of the defect or damaged tissue.

The selvedge edges are usually made of braided dacron and if the woundbecomes infected, the selvedge edges retain infection because of themultiple filament yarn construction of the selvedge edge. This resultsin prolongation of the wound infection and frequently infected drainingsinus tracts originating from the selvedge edge develope. This requiresfurther surgery to remove the infected selvedge edge.

FIGS. 2 and 2A are photographs of continuously knitted tubular surgicalmesh of the present invention. There is no selvedge edge provided alongthe border or edges of each side of the strip of mesh, the continuousknitted border edges being sufficient to prevent unraveling or frayingof the border edges as a result of suture tension and at the same timeavoid retaining any infection present by the border edges such as in thecase of strips of surgical mesh requiring selvedge edges as in the priorart and as illustrated in FIG. 1.

The surgical mesh is woven or knitted of monofilament threads free ofwater-leachable irritant impurities such as anti-oxidents and catalystresidues in order to prevent irritation and inflammation of animaltissue. In addition, the monofilament threads must be physiologicallyinert and non-irritating even in the presence of infection. The threadsshould be strong enough to withstand the conditions of use, for example,have a tensile strength of at least 50 psi.

The tubular surgical mesh is knitted in a continuous tubular shape withthe threads being unattached to each other and nonmechanically joined attheir points of contact or crossing which result in the mesh beinghighly pliable and having good stretch and flexibility.

A monofilament having a diameter of 5 to 15 mils and 10 to 20 stitchesor courses per inch can be employed. A preferred tubular mesh ispolypropylene having a diameter of 10 mils, 14 wales per inch, 15stitches per inch, weighing 2.4 oz. per yard, and a 3 course atlas fullythreaded Raschel chain notation 2/0-2/4-4/6-3/2, with no selvedge edge.

Any type of continuous knitting which would provide a tubular mesh asindicated above can be employed to make the surgical mesh. For example,double bar knit and double needle raschel fabric are satisfactory.

Any monofilament thread can be used which is free of water-leachableirritant impurities and is physiologically inert even in the presence ofinfection. At the present time polypropylene monofilament is preferred,but the surgical knitted tubular mesh can be woven from othermonofilaments, such as dacron, teflon, or polyethylene monofilament.

For a further description of suitable monofilaments, their manufacture,and weaving or knitting of surgical mesh suitable for use in the presentinvention, reference is made to my prior U.S. Pat. Nos. 3,054,406 and3,124,136. Accordingly, no further description is given or deemednecessary of the particular monofilament, its manufacture, or theknitting and the knitting parameters.

The tubular mesh may be knitted in a variety of sizes, that is widths of1 inch, 11/2 inch, 2 inch, 3 inch, 4 inch, 6 inch, 8 inch, 10 inch andlarger, as desired and necessary.

The tubular mesh provides substantially increased porosity and hencesubstantially increased tissue growth through it and substantiallydecreases incidents of infection over the flat mesh and yet at the sametime is flexible and has improved tensile strength and flex properties.For example, an 8 mil tubular mesh has 19 stitches to the inch whichprovides approximately 30% more porosity than a 6 mil flat mesh whichhas 68 stitches to the inch, and a 10 mil tubular mesh having from 10-15stitches to the inch provides greater than 50% more porosity than a 6mil flat mesh, thus substantially enhancing the growth of tissue throughthe tubular meshes.

The following Table I illustrates the results of tensile tests onpolypropylene surgical mesh samples consisting of a flat 6 milpolypropylene monofilament having a dacron selvedge edge with tubular 8and 10 mil polypropylene monofilaments.

                  TABLE I                                                         ______________________________________                                        LENGTHWISE                                                                         TYPE     LENGTH    YARN   POUNDS  POUNDS                                 ______________________________________                                        A-1  Flat     1"        6 mil  7.7     46                                     A-2  Flat     2"        6 mil  5.4     59                                     B-1  Tubular  1"        8 mil  144     144                                    B-2  Tubular  2"        8 mil  250     277                                    C-1  Tubular  1"        10 mil 220     220                                    C-2  Tubular  2"        10 mil 294     294                                    D-2  Tubular  2"        10 mil 237     260                                    ______________________________________                                        CROSSWISE                                                                          TYPE     WIDTH     YARN   POUNDS  POUNDS                                 ______________________________________                                        A-2  Flat     2"        6 mil  43      69                                     B-2  Tubular  2"        8 mil  34      60                                     C-2  Tubular  2"        10 mil 29      66                                     D-2  Tubular  2"        10 mil 32      66.5                                   ______________________________________                                    

The tension property was determined as pounds pulled at first break andfinal break at a pulling speed of 2"/min. Testing was done on InstronUniversal Test Machine.

In the foregoing Table I, it is the 2nd break that is of importance inuse. The 1st break merely consists of a beginning of an unraveling. Itis seen that in the Lengthwise tensils test results, the tubular meshhas a tensile strength considerably greater than that of the flat mesh.

In the Crosswise testing, the difference is not so great as the cut edgeof the tubular mesh begins to unravel. In use, the tubular mesh isstitched along its folded and uncut portion, as described subsequently.

The following Table II sets forth the tension and flexural properties ofpolypropylene surgical mesh. The samples are coded the same as they arein Table I for comparison purposes.

                                      TABLE II                                    __________________________________________________________________________    TENSION AND FLEXURAL PROPERTIES ON                                            POLYPROPYLENE SURGICAL MESH                                                            Flat 6 mil                                                                          Flat 6 mil                                                                          Tub 8 mil                                                                           Tub 8 mil                                                                           Tub 10 mil                                                                          Tub 10 mil                                      A-1"  A-2"  B-1"  B-2"  C-1"  C-2"                                   __________________________________________________________________________    Pounds at Break                                                               Longitudinal                                                                  First Break                                                                             8     5    144   254   220   267                                    Final Break                                                                            46    59    144   277   220   294                                    Transverse                                                                    First Break                                                                            --    45    --     19   --    217                                    Final Break                                                                            --    56    --     50   --    265                                    Flexes to Failure                                                                             426,000*   1,100,000   1,100,000                                             or                                                                            526,000                                                                 RESAMPLES                                                            Pounds at Break                                                               Longitudinal                                                                  First Break                                                                             7    28     79   210   151   193                                    Final Break                                                                            42    60    113   238   173   281                                    Transverse                                                                    First Break                                                                            --    43    --     34   --     29                                    Final Break                                                                            --    69    --     60   --     66                                    __________________________________________________________________________     Broke overnight  could have been 420,000 + 6,000 or 420,000 + 106,000.   

The flexural property of the samples in Table II was determined asnumber of flex to break using an MIT Folding Endurance Tester with 1.5kg load and bending arc of 235°.

From the foregoing Table II it is readily seen that the tubular mesh hassubstantially increased flexural properties over that of the flat mesh.

Referring now to FIGS. 3, 4 and 5, the use of the continuously knittedtubular surgical mesh of the present invention is illustrated inrepairing incisional hernias.

In the repair of the incisional hernia, the hernial sac is dissected outand excised. The anterior fascia of the hernia ring is dissected free ofsubcutaneous fat for a distance of 1.5 inches circumferentially.

To serve as a retractor, a dinner plate, salad plate, or saucer(sterilized by autoclaving and not shown) is placed in an invertedposition in the abdominal cavity to cover the bowel and omentum and toserve as a deflector for the mattress sutures to be placed through themusculofascial layer and peritoneum. The size of the plate is determinedby the size of the defect. The largest plate that can be insertedthrough the hernial ring is selected. The inverted plate serves as anexcellent weight retractor for the bowel and other viscera and makes therepair much easier. The plate, not shown, is removed just before pullingup and tying the sutures on the second side of the hernial ring. Thetagged sutures on the second side of the repair must be left long at thetime of placement to allow removal of the plate before closure of thesecond side.

As illustrated in FIG. 3, a two inch strip of a continuously knitted,tubular, surgical mesh of monofilament threads is flattened therebyproviding continuous knitted border edges on each side of the mesh, freeof selvedge edges, which is then sutured beneath the posterior aspect ofthe hernial ring, running the strip in the long axis of the defect andusing suitable mattress sutures, such as no. 1 polypropylenemonofilament. This is accomplished, as illustrated in FIG. 3, by firstsuturing the mesh below one edge, spacing the sutures 0.5 inch apart and1.5 inches back from the edge of the hernial ring. The mattres suture isplaced as a Lembert suture so that the closed loop lies at a right angleto the line of closure. This provides better spacing of the sutures andlessens the tendency of the mattress suture to cut through the tissue.

After all sutures have been placed and tied on one side, a mattresssuture is placed at each end of the hernial defect (only one end beingshown), passing through the ends of the 2 inch strip of tubular surgicalmesh. These two sutures close the two ends of the defect.

As illustrated in FIGS. 3 and 4, mattress sutures are next placed on theopposite side of the defect to complete the closure. These sutures areplaced and tagged with hemostats before tying because of limitedaccessibility. As best illustrated in FIG. 4, the sutures are placed 0.5inch apart and 1.5 inches back from the hernial edge as on the opposingside.

To obtain even spacing of the sutures it is best to place them by"halving," that is, one at each end of the hernia defect, one in themiddle, and so on until sufficient sutures have been placed to allowspacing of 0.5 inch between sutures. After all sutures have been placedand tagged, they are pulled up, held by the surgeons' assistant, andtied by the surgeon. It is best to have all the sutures pulled up at thesame time, the assistant maintaining traction on them while the surgeonties. In very large defects, it is desirable to have second and thirdassistants push in on the flank of the patient to achieve approximationof the hernial edges while the sutures are being tied.

Finally, and as illustrated in FIG. 5, a continuous suture is used toclose the anterior fascia in the midline, over the mesh, such as with asuture of no. 0 polypropylene monofilament. If the mattress sutures havebeen correctly spaced (1.5 inches back from the hernial edge on eachside), the musculofacial borders of the hernial ring should closewithout tension. This completes the repair.

Redundant skin and subcutaneous fat are then excised from both sides toallow a snug closure and eliminate dead space. Suction drains (closeddrainage) are then placed subcutaneously to avoid any possiblecollection of blood postoperatively, the drains normally being left inplace three to four days.

The foregoing is a preferred incisional hernia technique utilizing aknitted tubular surgical mesh of the invention. Other techniques, ofcourse, can be used and in general, the tubular mesh can be used whereall the other meshes have been utilized in the past with improvedresults. This includes not only incisional but inguinal hernias and toclose defects in the abdominal and chest walls.

In general, a 11/2 inch tubular mesh is preferred for incisionalhernias, using the technique described above, and a 1 inch tubular meshis used for inguinal hernias. My article in Surgery, Gynecology andObstetrics, September, 1970, vol. 131, 525-530 describes a technique forrepairing incisional hernias utilizing the prior art flat mesh withselvedge edges which can be employed with the tubular surgical mesh ofthis invention.

Operations have been preformed upon three large incisional hernias inwhich the prior surgical mesh provided with selvedge edges asillustrated in FIGS. 1 and 1A, had been used with complete breakdown andreoccurrence. These were reoperated and the tubular mesh was used, asdescribed above and the results have been excellent. No reoccurrences orwound complications in 60 such cases to the present time.

In addition, in another patient a one inch surgical mesh of the priorart as illustrated in FIGS. 1 and 1A, was removed because the woundbecame infected and drained for 21/2 weeks. The mesh with the selvedgeedges was removed and the wound healed. A reoccurrence then developedbecause of the breakdown of the repair, and the inguinal hernia wasrepaired using a one inch tubular mesh according to the inventionwithout problem and the patient was cured.

In the repair of hernias, such as incisional and inguinal hernias anddefects in the abdominal and chest walls, it is important to promotegrowth of the tissue through the mesh to provide additional strength tothe repaired area. Referring now to FIG. 6, which is a photograph of adog with an incisional hernia on its left side having the surgical meshof FIGS. 1 and 1A of the prior art sutured in place. The mesh waspurposely infected and the hernia closed.

The surgical mesh of the present invention as illustrated in FIGS. 2 and2A was sutured in the left side of the dog, deliberately infected, andthe incisional hernia closed. Eighteen days later the right and leftsides were opened and, as illustrated in FIG. 7A, the tissue had growncompletely through the tubular surgical mesh thereby providing goodtissue growth and strength to the damaged area, and as illustrated inFIG. 6A, very little tissue had grown through the prior art mesh on theleft side.

In short, the advantages of the tubular surgical mesh of the presentinvention are: (1) it is stronger in tension and flexure than thesurgical mesh of the prior art because of its two layer openconstruction; (2) it is possible to provide a more open weave, moreporous mesh than the surgical mesh of the prior art, which permits morerapid tissue growth through it and lessens the change of potentiatinginfection; (3) it has no selvedge edge which potentiates infection; (4)it has much greater two way stretch than does the prior surgical meshwhich is of tremendous aid to the surgeon technically in both incisionaland inguinal hernias. There are do disadvantages of the tubular meshcompared to the prior surgical mesh of which the inventor is aware.

Accordingly, the present invention is well suited and adapted to attainthe objects and ends and has the advantages and features as mentioned aswell as others inherent therein.

Whhile presently preferred embodiments have been given for the purposeof disclosure, changes can be made therein which are within the spiritof the invention as defined by the scope of the appended claims.

What is claimed is:
 1. A surgical mesh of monofilament threads free ofwater-leachable irritant impurities and being physiologically inert evenin the presence of infection,having a tensile strength sufficient whendoubled to withstand wound tension, the threads in the mesh having adiameter in the range of 5 to 15 mils, the mesh having 10 to 20 stitchesper inch and being knitted in a continuous tubular shape with thethreads being unattached to each other at their points of crossing, themesh being flattened in use thereby providing continuous suture borderedges on each side of the mesh free of selvedge edges.
 2. The surgicalmesh of claim 1 where,the threads are polypropylene monofilament.
 3. Thesurgical mesh of claims 1 or 2 where,the threads have a diameter of 8 to10 mils, and the monofilament is polypropylene.